A rotary electrical machine comprises a rotor which is mobile in rotation, and has a constant machined outer diameter. This rotary electrical machine additionally comprises a fixed stator which surrounds the rotor. The rotor and the stator are separated from one another by an air gap with a constant width. When the rotor is rotating, it induces a magnetic field on the stator, which transforms this field into electric current in order to supply the electronics of the vehicle and recharge the battery.
In addition, motor vehicles have electrical energy consumption which is increasingly great, and the rotary electrical machines are therefore required to have increasingly high performance, in order to provide the electrical energy necessary. A solution to improve the performance of a rotary electrical machine is to increase the speed of rotation of the rotor. In fact, this makes it possible to increase the output of the rotary electrical machine.
However, increasing the speed of rotation amplifies the centrifuging effect corresponding to the mechanical deformation of claws of the rotor. Because of the centrifuging, the claws of the rotor could then rub on the inner diameter of the stator, and thus destroy the rotary electrical machine, or at least damage it.
In order to avoid the risks of friction between the rotor and the stator, the width of the air gap must then be increased. However, increasing this width amounts to moving the rotor away from the stator, which gives rise to a decrease in the performance of the rotary electrical machine.